CAR-T cell therapy for pediatric solid tumors: armored CAR-T cells and beyond

CAR-T cell therapy, which uses endogenous T cells engineered to target specific cancer antigens, is one of the most promising recent developments in the treatment of hematologic malignancies in both children and adults. CAR-T cells have shown tremendous success in treating B-cell lymphoma, acute lymphoblastic leukemia, and multiple myeloma, and they are currently FDA-approved for the treatment of six hematologic malignancies. Its success in solid tumors has been more modest, which has been attributed to several factors including the hostile tumor microenvironment (TME), poor persistence of CAR-T cells, and difficulty directing CAR-T cells towards solid tumors. Armored CAR-T cells, which modify the TME via secreted cytokines, have shown early success in the treatment of solid pediatric malignancies. We review recent trials of CAR-T cells to treat common pediatric solid malignancies, including Ewing sarcoma, osteosarcoma, neuroblastoma, diffuse intrinsic pontine glioma, rhabdomyosarcoma, Wilms tumor, and retinoblastoma. We focused particularly on armored CAR-T cells where applicable. Armored CAR-T cells have been utilized to target a variety of tumor-associated antigens on pediatric solid tumors with early successes both in vivo and in vitro, and innovative approaches for addressing their limitations are rapidly being developed.